To get a dial in number added to your invites, you must have an audio conferencing license. Only the organizer of the meeting needs this license. Once applied to your account, when you create a Teams meeting, the dial in number will appear on the invite. Also, this will give users the capability to use the call me back feature.
Many users who have scheduled WebEx meetings in the past already have this license applied to their accounts. If you do not see a dial in number when you create a Teams meeting, please reach out the help desk to request a license. It requires manager approval.